266 BARKS 



The student should carefully compare the principal varieties of 

 cinchona bark and note the following prominent characters : 

 1. Quilled barks : 



(a) G. succirubra ; longitudinal wrinkles and reddish warts ; 



a more or less spongy bark. 



(6) C. Calisaya ; longitudinal furrows, transverse cracks, 

 cork often exfoliating ; a firm hard bark. 



(c) G. officinalis ; very numerous small transverse and longi- 



tudinal cracks ; quills usually very small and rough to 

 the touch ; a firm bark. 



(d) C. lancifolia ; more or less uniformly smooth surface with 



patches of silvery-grey cork. 



I'IG. 135. Bark of Cinchona lancifolia, showing patches of 

 silvery cork. Natural size. 



(e) G. Ledgeriana ; cracks more numerous than in G. Calisaya ; 

 bark rougher. 



2. Flat barks : 



(a) G. succirubra ; ferruginous red colour, reddish warts, and 



raised ridges ; usually in thick pieces. 

 (6) G. lancifolia ; exhibits the characteristic silvery cork. 

 (c) C. Calisaya ; thick pieces with a wavy fibrous surface 

 exhibiting depressions. 



Constituents. The chief constituents of cinchona barks are the 

 alkaloids they contain, of which a number have been isolated. Some 

 of these are well-defined crystalline substances ; some have been 

 obtained only in an amorphous condition ; of others it is question- 

 able whether they are not produced from other pre-existing alkaloids 

 during the process of isolation. 



The principal alkaloids in cinchona are quinine, cinchonidine, 

 cinchonine, and quinidine ; next in importance are hydroquinine, 



